In the confusion, passengers who had already been screened were mixed with people who had not been through the security process.

The airport therefore made the decision to cancel all flights until midnight for safety reasons.

The spokesperson said: “[It all happened] right next to the check in desk.

“The smoke was billowing into the terminal so we had to evacuate passengers to a safe area. Initially it was not known what the cause of the incident was – so we had to move passengers into a departure lounge. That meant taking them past the security area into the departure lounge so they mixed with the people who hadn’t been through the security process.

“This took a long time. Flights needed to be cancelled to [protect] the next wave of flights.”

He added that the current advice for passengers who had flights cancelled or delayed was to contact their airline or make a claim on their travel insurance.

A number of passengers took to Twitter to voice their dissatisfaction as their plans for Easter weekend went up in flames.

I honestly don't know who made all the calls tonight at #Stansted but that was so poorly managed. Bloody chaos and putting people through so much hell for nothing. No one got to fly! A bus caught on fire outside the building. Why did everything else fall apart?! pic.twitter.com/tfKkvRH9C8

Bo Marit said: “Easter weekend flight cancelled due to #Stansted fire. I don’t often do this, but: the airport evacuation procedure and organisation was appalling, and if anything worse had happened it would’ve been catastrophe. That’s a busy airport. Sort it out before people get hurt.”

Joe Cashman added: “Going down the runway at Stansted then turned around and now must get off the plane because there was a bus on fire 45 minutes earlier. This is some joke #stansted #fire #StanstedAirport The planes already boarded could have been let fly at least.”

However another user, Sophie, was more sympathetic. She tweeted: “I don’t think some people who are b**ching and whining about the situation at #stansted have any idea of what an airport/airlines have to do in the event of a fire. So many protocols, many of which are more important than your holiday or business trip.”

Speaking yesterday afternoon, a spokesman for Essex County Fire and Rescue Service said: “Firefighters are currently at the scene of an incident at Stansted Airport.

“Crews reported on arrival that a bus, positioned outside the terminal entrance, was well alight.

“Due to the volume of smoke, the terminal was partially evacuated while firefighters extinguished the fire.”

He added the fire was extinguish by 5.02pm although fire crews remained on the scene for some time after, using thermal imaging cameras to make sure there are no remaining hotspots.

A fire spokesman later added: “The bus has been completely destroyed, while much of the front of the terminal building has suffered smoke damage.

“We believe the fire was caused accidentally by an electrical fault on the bus.”

An update posted on the airport’s Twitter feed at 11.30pm read: “Following the earlier incident involving a shuttle bus fire on the terminal forecourt, we confirm that the Airport will be open tomorrow and flights are expected to operate as normal.

“Passengers are advised to check the latest flight information with their airlines.”

This morning’s first flight left Stansted on time at 6am.

The spokesperson for Stansted Airport added: “The airport was alerted to a major fire on a transfer bus outside the entrance to the terminal building at 4.20pm on Friday, March 30. The fire was caused by an electrical fault on the bus and was brought under control within 20 minutes by the emergency services. Passengers were quickly evacuated away from the fire and there were no reported injuries.

“As a result, a number of flights were delayed, cancelled or diverted to other UK airports. Our terminal team and additional staff have worked around the clock to provide welfare assistance to those passengers who were affected by the flight cancellations. We apologise to those passengers who were affected and can confirm that the airport will be open today (March 31) with all flights expected to operate as normal.”